Hi grwalker. I've experienced the same shifted recurring events on my BB also. This is what I found out.

For any recurring event, there is a start date.

For a recurring birth day event, the start date is usually the individual's birth date.

If a person was born before 1970 (for example, birth date/start date=Mar.1.1969), that person's recurring birth day event will have a start date before the year of 1970.

For a recurring event with a start date before the year of 1970, when synced from Google Calendar to the BB Calendar, its date will be shifted (probably according to some formulas)

You can prevent the shifting by altering the start date of the recurring birth day event so that the start date is on or after the year 1970 (for example, birth date/start date=Mar.1.1969 should be changed to Mar.1.1970)

It's a clumsy fix but it WILL fix the shifting problem.

Google wireless sync of calendar and contact via BIS is a mess. Don't get me started with the contact wireless syncing problem. Address fields got lumped together. First name and Last name fields are NOT mapped correctly, etc...